Light as an ecological factor and its measurement

Abstract

Refinement in knowledge and new scientific discoveries follow closely behind the introduction of new scientific instruments and new scientific techniques. And in no phase of botany has this been more evident than in the general field of plants in relation to light. Of outstanding importance has been the general availability of cheap reliable light-measuring devices that use as their sensitive element the photoelectric cell. Equally important have been the advances made in growing plants in controlled environment through the use of newly developed artificial sources of light, particularly the neon and sodium vapor lamps and the filters that transmit definite ranges of wave lengths. As a result recent workers have been able to surpass their predecessors in the accuracy of light measurement and in the precision of light control. And through advances in experimental design and statistical analysis developed by Professor R. A. Fisher and his American disciples (55, 156) they have learned how to analyze the separate and combined effects of varying several factors simultaneously in the same experiment. All three of these developments appeared before 1935 when the original paper under this title was published (148), but had not yet been put to widespread use in botanical research. Just as the trends in research might have been predicted ten years ago on the basis of new light sources, new light measurement devices and new experimental design and analyses, so today we may predict that advances in understanding the relationship of light to plants during the coming ten years will result from a more widespread use of fluorescent light sources and the introduction of heavy carbon as an indicator element in photosynthesis. We may expect further refinement of the mathematical relationships between total available light and plant growth as a result of the increased general availability of light recorders.